All ye who are computer savvy HELP!!!

Hello,

I am so frustrated!!! I bought a new laptop (was a floor model but is in great shape as far as I know) and let the technicians at the computer store install all I needed to make it user ready. I got it at Christmas time. It is an ACER. I have wireless internet in my home through AT & T. I have only used the computer a couple of times and my daughter adds things as I need them. There isn't a whole lot on it except microsoft office and such and pics. It was working and would connect to the internet, but now it won't. The last thing my daughter remembers doing to it is installing my IPOD software and installing a cd of pics I got from a picture studio. Now it won't connect. We have tried everything we can think of. It states that the settings saved on the computer for the network do not match the requirements of the network or the capability of your network adapter does not match the requirements of this network. It was working fine before, so I'm at a loss. Can anyone help?? Thank you